Binary Search Tree [Selise]

#include<bits/stdc++.h>
using namespace std;

struct BstNode
{
    int data;
    struct BstNode *left, *right;
}*root = NULL;

class BST_Tree
{
public:

    BstNode *insert_node(BstNode *root, int data)
    {
        BstNode *newnode = new BstNode;
        newnode -> data = data;
        newnode -> left = newnode -> right = NULL;

        if(root == NULL)
        {
            root = newnode;
            return root;
        }
        else if(data <= root -> data) root -> left = insert_node(root -> left, data);
        else root -> right = insert_node(root -> right, data);
        return root;
    }

    bool Search(BstNode *root, int data)
    {
        if(root == NULL) return false;
        else if(root -> data == data) return true;
        else if(root -> data >= data) Search(root -> left, data);
        else Search(root -> right, data);
    }

    void Inorder_traversal(BstNode *root)
    {
        if(root != NULL)
        {
            Inorder_traversal(root -> left);
            cout << root -> data << " ";
            Inorder_traversal(root -> right);
        }
    }


};

int main()
{
    BST_Tree tree;
    root = tree.insert_node(root, 10);
    root = tree.insert_node(root, 12);
    root = tree.insert_node(root, 167);
    root = tree.insert_node(root, 19);
    root = tree.insert_node(root, 45);
    root = tree.insert_node(root, 8);
    tree.Inorder_traversal(root);
}